C. - Granulométries et minéraux lourds / Granulometry and heavy minerals

Sands of the Tunisian shelf consist of a mixture in different proportions of bioclasts, generally prevalent, and quartz grains. Quartz is concentrated along shore lines, modern and ancient. Comparison of grain size analysed before and after acid treatment shows ; ; 1 ) an interaction between quartz and carbonate grains during transportation ; ; 2) that coastal sands are well sorted and clean ; ; 3) that sands of meadows range from well to poorly sorted and from clean to highly muddy ; ; 4) that neritic sediments deposited at present mostly consist of mud. Grain size analyses of bioclasts can be helpful in recognizing ancient environments.